1. Field
This invention concerns coal or other type mine ventilation systems wherein fresh air is forced into the mine, typically thru its main gallery or shaft entrance or down thru vertical shafts or other passages, and is then directed by air flow barriers or stoppings of some sort deep into the main shaft or into branch shafts off of the main shaft. Such shafts often extend for miles into the earth in vertical. slanted or horizontal directions to follow the seams being mined.
In order for the ventilation air to be effective in both bringing oxygen and other necessary gasses to the work areas such as around the seam face, and then to evacuate worker respiration gasses such as CO and CO.sub.2, mine gasses such as methane, and equipment fumes or the like from these areas, an actual ventilation channel must be established such that incoming and outgoing air are not inteniixed to a point where, e.g., O.sub.2 concentration within the work area drops to a level unable to sustain proper respiration.
These barrier devices are used not Vonly to control and direct air flow but also to seal off portions of a mine no longer being worked or temporarily shut down. The barriers are typically installed in such a manner as to direct air flow to the working face and to stop air flow through cross cuts and entries which are not being worked. The ventilation air to be delivered under pressure to the working face can originate at a considerable distance from the face, and therefore, stoppings or barriers separating the crosscuts and entries must be substantially air-tight to prevent air flow losses which would significantly reduce the velocity of the air flow at the mine face. Such flow losses can easily diminish by half the induced air, simply through leaky stoppings and doors. Consequently, the dust and gases in the work area will not be effectively transported to the mine exit.
2. Prior Art
Heretofore, various air flow directing barrier, stoppings or brattice structures and techniques have been employed for constructing ventilatiton passages within mines as exemplified and described in U.S. Pat. Nos. 4,1880,352 and 4,516,879, the disclosures of which are hereby incorporated herein bv reference in their entirety. The structure of these patents are effective, to varying degrees, in directing air flow within mines. however, they suffer--in a practical sense--from being too expensive or complex to manufacture, to transport to and within the mine, to install, or in some cases to operate, such as roll-up curtains or the like. Also, under present Federal and State mining equipment standards, some of these prior structures cannot meet the rigorous requirements, e.g., of fire resistance and lateral impact strength.
As stated succinctly in U.S. Pat. No. 4,516,879, - - - "The construction and maintenance of mine stoppings is expensive and time consuming. Conventional stoppings consist of wsalls constructed of concrete block and cement, which are relatively difficult and costly to construct and maintain. For example, a typical coal mine stopping consists of about 160 concrete blocks, and at least one mining car is usually required to transport construction materials significant distances down into the mine to erect one mine stopping. Furthermore, a substantial amount of time and manpower is also required to construct such a mine stopping since each of the concrete blocks have to be individually set in place and cemented.
The rigidity of a mine stopping of this type makes it susceptible to deformation by convergent ground movements or shock from explosive charges. Failure of the stopping is manifested by the formation of the aforementioned air leaks or, in the worst case, by a total collapse of the masonry structure, thereby requiring reconstruction of the stopping in the operational maintenance of the mine ventilation svstem The elimination or reduction of stopping air leakage and of stopping failures is essential to the provision of a satisfactory ventilation efficiency in the mine, with resulting health and sanity benefits to the miners."